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Headshot of Emily Lakdawalla

Just what is going on in that magnificent Cassini image of Saturn?

Posted By Emily Lakdawalla

13-11-2013 15:58 CST

Topics: pretty pictures, Cassini, podcasts and videos, Saturn's small moons, Saturn's moons, Saturn, Saturn's rings

It took months of work (and no wonder) but the wait was worth it: here is Cassini's spectacular view of Saturn, captured on July 19, 2013, as Cassini passed through Saturn's shadow.

In Saturn's Shadow (The Day the Earth Smiled)


In Saturn's Shadow (The Day the Earth Smiled)
On July 19, 2013 Cassini passed into Saturn's shadow and turned toward the Sun, capturing an image of the planet's night side and the weirdly lit semi-transparent rings. Cassini also captured seven of the moons and three planets. This was the third time our home planet was imaged from the outer solar system; the second time it was imaged by Cassini from Saturn's orbit; and the first time ever that inhabitants of Earth were made aware in advance that their photo would be taken from such a great distance.

This photo is amazing, but also confusing. I thought I would try to explain some of the cool stuff you can see with a little video demonstration:

Emily Lakdawalla of the Planetary Society reveals the hidden features of this spectacular photo mosaic of the planet Saturn, as seen by NASA's Cassini mission in 2013.

It's also interesting to compare the photo to a similar one, taken in 2006, with the rings tilted the other way.

In Saturn's Shadow (2006)


In Saturn's Shadow (2006)
With giant Saturn hanging in the blackness and sheltering Cassini from the sun's blinding glare, the spacecraft viewed the rings as never before, revealing previously unknown faint rings and even glimpsing its home world.
See other posts from November 2013


Read more blog entries about: pretty pictures, Cassini, podcasts and videos, Saturn's small moons, Saturn's moons, Saturn, Saturn's rings


Patrick Noonan: 11/13/2013 04:38 CST

Wonderful explanation - thanks for taking the time and trouble to do it. I was indeed having trouble making sense of the complex geometry represented in that fantastic image, and now it's clear!

Bernard: 11/13/2013 05:16 CST

Thanks Emily. I'm guessing it wasnt just me who was having trouble making sense of the image. That has certainly helped.

Todd Howard: 11/13/2013 05:25 CST

Thanks for a really clear walk-through tour of what we're actually seeing, and (in my case) might be missing too.

Messy: 11/13/2013 09:02 CST

no wonder it made the front page of the New York TIMES....

Sridhar: 11/14/2013 11:30 CST

This was absolutely brilliant. Thanks so much for unpacking the details in this fabulous image.

Sameer Marathe: 11/14/2013 04:18 CST

Amazing image and very nice explanation of all the details. There is one this I don't understand, is this a single image (i.e. a single exposure) or a stitching together of multiple exposures? Phil Plait in his blog post says that it was a collection of images taken over 4 hour period that were later put together into this one picture. Since Cassini is in orbit, it's relative position with respect to Saturn must have changed over this time. How was that accounted for and why don't we see any distortion or other effects because of that? Were the images somehow corrected for the change in vantage point?

Chris Campbell: 11/15/2013 10:25 CST

Sameer: it is indeed a mosaic of many photos. While the spacecraft is moving, the orbit is quite large and it's moving relatively slowly. But even if there is some parallax movement, it's a straightforward task for the imagery scientists to process that. See this video (cued up to the right spot) for a little more info from July when this photo sequence was being anticipated. I waved :) And you might also be interested in this overview of the orbits, the mission plan:

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